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3 years ago

Answer this plz to be rater 5 stars

Mathematics

1 answer:

mr Goodwill [35]3 years ago

4 0

Answer:

Step-by-step explanation:

3 min 20 seconds = 3*60 + 20 = 180 +20 = 200 seconds

2 min 44 seconds = 2*60 + 44 = 120 + 44 = 164 seconds

Improvement = 200 - 164 = 36 seconds

Percentage =(36/200) *100

= 18 %

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3 years ago

Solve the equation by using square roots. 2 x 2 − 9 = 11

VashaNatasha [74]

Answer:

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Step-by-step explanation:

Given

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Simplify 6 - 4[x + 1 - (y + 3)] + 5y

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AVprozaik [17]

Answer:

The 99% confidence interval would be given by (196.2;283.8)

We are 99% condident that the true mean is between 196.2 and 283.8

We need to assume that the data comes from a random sample and we need to assume that the distribution of the data is normal.

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$\bar X=240$ represent the sample mean for the sample

$\mu$ population mean (variable of interest)

s=15 represent the sample standard deviation

n=4 represent the sample size

Part a

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

In order to calculate the critical value $t_{\alpha/2}$ we need to find first the degrees of freedom, given by:

$df=n-1=4-1=3$

Since the Confidence is 0.99 or 99%, the value of $\alpha=0.01$ and $\alpha/2 =0.005$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.005,3)".And we see that $t_{\alpha/2}=5.84$

Now we have everything in order to replace into formula (1):

$240-5.84\frac{15}{\sqrt{4}}=196.2$

$240+5.84\frac{15}{\sqrt{4}}=283.8$

So on this case the 99% confidence interval would be given by (196.2;283.8)

We are 99% condident that the true mean is between 196.2 and 283.8

What assumption about the data is necessary for the inference derived from the analysis to be valid?

We need to assume that the data comes from a random sample and we need to assume that the distribution of the data is normal.

4 0

3 years ago

Worth 17 points! Help me please!!! Look in the picture

ivanzaharov [21]

Answer:

Part A

1. After 4 weeks of work, Jeremy has saved 300

2. Jeremy worked 8 weeks in order to save $600

3. For every one week of work, Jeremy saved 75 dollars

4. If Jeremy works 15 weeks, then he can expect to save 1,125 dollars

Part B

1. Saeed orders 15 meals and his total cost of delivery is $24

2. Saeed paid $32 to have 20 meals delivered

3. For every meal delivered, Saeed is charged $1.6

4. If Saeed pays $19.20 in delivery fees then he ordered 12 meals

Step-by-step explanation:

Part A

The given graph gives the proportional relationship between total amount saved and the number of weeks worked

1. Reading from the graph, at the point where the vertical line from point 4 touches the line of the graph, an horizontal line to the vertical y-axis touches the y-axis at 300

Therefore;

After 4 weeks of work, Jeremy has saved 300

2. The point where an horizontal line from point 600 on the vertical y-axis touches the line of the graph, a vertical line drawn to the horizontal, x-axis touches the x-axis at 8

Therefore;

Jeremy worked 8 weeks in order to save $600.

3. The rate of change of the amount saved to the number of weeks worked, 'm', for the given proportional relationship (straight line relationship, passing through the origin) is given as follows;

Rate of change, m = Constant = y/x

∴ Rate of change of the amount saved to the number of weeks worked = (300-0)/(4 weeks- 0 week) = 75/week

Therefore;

For every one week of work, Jeremy saved 75 dollars

4. The amount Jeremy would have saved in 15 weeks, 'A', is given as follows;

A = m × n

Where;

m = The rate of change of the amount saved to the number of weeks worked = 75/week

n = The number of weeks worked

∴ A = 75/week × 15 = $1,125

Therefore;

If Jeremy works 15 weeks, then he can expect to save 1,125 dollars

Part B

From the graph, we have;

1. From the graph there is a proportional relationship between the total cost of delivery and the number of meals

At the point a vertical line drawn to the line of the graph from 15 on the horizontal axis (number of meals), a horizontal line drawn to the vertical y-axis touches the y-axis at 24

Therefore;

1. Saeed orders 15 meals and his total cost of delivery is $24

2. From the point where the horizontal line from 32 on the vertical axis touches the linear graph of the relationship between the total cost of delivery and the number of meals, a vertical line drawn down to the horizonal axis touches the horizontal x-axis at 20

Therefore;

Saeed paid $32 to have 20 meals delivered

3. The rate of change of the total cost of delivery to the number of meals, 'm', is given as follows;

m = y/x (for proportional relationships)

Taking any corresponding 'x' and y-values

m = 16/10 = 32/20 = 24/15 = 1.6 Dollars/meal

Therefore;

For every meal delivered, Saeed is charged $1.6

4. From m = y/x = 1.6

When y = $19.20

x = y/m = $19.20/($1.6/meal) = 12 meals

Therefore;

If Saeed pays $19.20 in delivery fees then he ordered 12 meals.

3 0

3 years ago